KR19990031917A - Method of adjusting brightness of image reader and its device - Google Patents

Abstract

Receives the reference data set by the user and compares the counting value counted at an arbitrary period.If the comparison result is the same, the counting value is converted into a time value, and then an optical signal input to the image sensor corresponding to the converted time value. Adjust the brightness of the image by adjusting the accumulation time.

Therefore, since the brightness is adjusted by changing the light signal accumulation time of the light source in proportion to the output voltage of the image sensor, accurate brightness can be adjusted to reflect the characteristics of the light source, and no additional correction is required according to the change of the light source over time.

Description

Method of adjusting brightness of image reader and its device

The present invention relates to a brightness adjusting method and an apparatus of the image reader, and more particularly, to improve the quality of the read image by making it possible to adjust the brightness of the image read by the image reader step by step It relates to a brightness adjustment method of the odor and its device.

In general, an image reader is a device that reads an image recorded in a document using light generated from a light source and a CCD (Charge Coupled Device), which is used for core parts of office automation equipment such as facsimile machines, copiers, and multi-function devices. This is generally called a scanner.

Referring to the general operation of the image reader, when the light generated from the light source is reflected on the image of the original, the amount of reflected light is converted into an electrical signal through the photoelectric conversion element, thereby reading a line of the original image. . In order to read one page of the original image, it is necessary to transfer the original at a predetermined interval or move the optical module of the image reader at a predetermined interval, which can be realized by a step motor. . The analogue electrical signal output by photoelectric conversion from the CCD is converted into digital data. Next, the system controller receives the data in digital form and converts the read image data into appropriate correction data through preset reference data (lookup table) according to the brightness level of a predetermined step. The converted data is transmitted to the computer via the interface device of the computer, and the read image data is displayed on the monitor. Here, the system controller controls the light source, the step motor, and other circuit operations at an appropriate timing to control the overall operation smoothly.

Meanwhile, according to the first exemplary embodiment for adjusting brightness, the system controller stores reference data including an appropriate number of reference data according to a preset step. That is, before the read operation is performed according to the brightness level designated by the user, the reference data is recorded in the brightness adjusting unit, and the image data converted into digital data is converted into correction data corresponding to the brightness level and output. The circuit operates to enable real-time read operation. In this operation, the brightness can be adjusted only by the image reader without processing image data by a separate program.

On the other hand, as a second conventional embodiment, there is a method for performing a brightness adjustment step in a computer. That is, the document reader simply reads the original image and transfers it to the computer.The computer stores the read image data in an arbitrary storage space and sets an appropriate brightness adjustment step based on the image displayed on the monitor. The brightness adjustment is performed by converting the read image data into an appropriate brightness level through an execution program.

On the other hand, in the third conventional embodiment, when using a light source, that is, a halogen lamp using an AC power source, the amount of light of the light source is controlled by the average power control provided to the halogen lamp using the phase angle control method of the AC power source. There is a way to perform the brightness adjustment.

However, such a brightness adjustment method of the conventional image reader causes the following problems.

(1) When the brightness is adjusted in the digital domain, when the overall value is lowered to darken, the number of gradations that can be expressed decreases and the quality of the read image is reduced. You cannot respond properly.

(2) As in the case of the first embodiment of the related art, when the brightness adjustment unit performs the brightness adjustment through the brightness adjustment reference data, the reference data according to the brightness adjustment step must be stored in the ROM, which is a program and data storage area. According to the brightness adjustment step specified by the user, the operation of storing the reference data in the lookup table area of the brightness adjustment unit in the form of memory should be accompanied. For example, when reading image data in units of 8 bits, at least 256 bytes of memory should be configured in the brightness adjusting unit. If the brightness adjusting function is performed in N steps, 256 × N reference data are stored in the data storage area. Should be Therefore, a large amount of memory (ROM and RAM) is required, which increases the price of the product.

(3) As in the case of the conventional second embodiment, according to the brightness adjustment processing method by the computer's execution program, since a separate processing time is required after reading the image, the brightness adjustment result is read out. You can't immediately check it later. In addition, the light quantity change characteristic of the light source due to the change over time has to be measured using a separate equipment, and there is an inconvenience of repeating the process of calculating the correction data.

(4) As in the case of the conventional third embodiment, when the halogen lamp is used, heat generation is severe and consumes a large amount of power, so that it is difficult to apply to a small image reader, and the AC power is used for the phase angle control method. As a result, noise is generated and image quality deteriorates.

Accordingly, the present invention is to solve such problems, the first object of the present invention is to adjust the accumulation time of the amount of light detected by the light generated by the light source is reflected on the document in accordance with the brightness adjustment step, the time-lapse of the light source The brightness of the image reader is not affected by the change, the gradation range of the reading image is not reduced, and the brightness of the reading image is brighter, so that the contrast effect of black, white, or color is improved to improve the quality of the reading image. To provide a method of adjustment.

In addition, a second object of the present invention is to provide a brightness adjusting apparatus of an image reader configured to operate using photoelectric conversion characteristics of a sensor so that light emission characteristics of a light source can be applied to a brightness adjusting step.

1 is an overall block diagram of a brightness adjusting device of an image reader according to the present invention;

FIG. 2 is a detailed block diagram of the scanner controller and the sensor driver shown in FIG. 1;

3 is a detailed structural diagram of the image sensor shown in FIG. 1;

4A to 4E are operation waveform diagrams for driving an image sensor;

5 is a waveform diagram illustrating photoelectric conversion characteristics of a sensor.

<Description of the code | symbol about the principal part of drawing>

1: Scanner control unit 2: ROM

3: RAM 8: Image Sensor

9: sensor driver 18: timer

19: latch portion 20: counter

21: comparator 22: shift pulse generator

23: drive clock generator 24: photosensitive part

25: transmission unit 26: output unit

A feature of the present invention for achieving the above object is to convert the optical density of the original input to the image sensor into an analog image signal through a photoelectric conversion method, and after performing pre-processing, to convert to the digitized image data A brightness adjusting method of an image reader, comprising: an input step of receiving reference data set by a user; A comparison step of comparing the counting value counted at an arbitrary period with the reference data input in the input step; A conversion step of converting the counting value to a time value if the result compared in the comparing step is the same; And an adjusting step of adjusting brightness of an image by adjusting an accumulation time of an optical signal input to the image sensor in response to the converted time value.

Preferably, the comparing step generates a clock signal having a predetermined frequency, counts the clock signal to detect a counting value, and compares whether the detected counting value is equal to the reference data.

Preferably, the frequency of the clock signal corresponds to the division coefficient of the brightness adjustment step divided into a plurality so as to adjust the brightness of the image.

Preferably, the adjusting may include counting the clock signal to maintain the optical signal accumulating operation until the reference data and the counting value are the same, and if the reference data and the counting value are the same, the counting value. After initializing the operation, the optical signal accumulation operation of the image sensor is resumed.

Optionally, after performing the adjustment step,

And a setting step of setting and storing the reference data, and adjusts the brightness of the image in response to the set and stored reference data unless a user inputs the reference data.

On the other hand, another feature of the present invention is the image reader of converting the optical density of the document input to the image sensor into an analog image signal through a photoelectric conversion method, and after performing a pre-processing, the image reader A brightness adjusting device comprising: detecting a time value corresponding to reference data input by a user, and outputting a predetermined control signal for controlling an accumulation time of an optical signal input to the image sensor according to the detected time value Scanner control unit; And a sensor driver for controlling a driving state of the image sensor according to a predetermined control signal from the scanner controller.

Preferably, the scanner controller further includes a timer for controlling the start and end time of the accumulation of the optical signal in response to the reference data.

Preferably, the timer, the latch unit for latching the reference data for a predetermined time; A counter for receiving and counting a clock signal having a predetermined period; And comparing the reference data latched by the latch unit and the counting value counted by the counter with each other. If the reference data and the counting value are the same, a trigger signal having a predetermined period indicating the start and end of the accumulation of the optical signal. Generating a comparator and outputting the comparator to the sensor driver.

Preferably, the predetermined frequency of the clock signal corresponds to the division coefficient of the brightness adjustment step divided into a plurality so as to adjust the brightness of the image.

Preferably, the trigger signal includes a pulse signal of a period corresponding to one period of the pulse signal input to the counter.

Preferably, the sensor driver, the shift pulse generator for generating a shift pulse signal of a predetermined period by the trigger signal output from the comparator; And a driving clock generator for generating a driving clock of the image sensor in response to the shift pulse signal output from the shift pulse generator.

Preferably, the driving clock includes a first driving clock and a second driving clock, and the first driving clock and the second driving clock have a phase difference of 180 ° with each other so as to alternately read the pixels of the image.

Preferably, the driving clock includes a reset signal, and the image sensor initializes the accumulation state of the optical signal by the reset signal.

Hereinafter, a method of adjusting the brightness of an image reader and a preferred embodiment of the apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 shows the overall block diagram of the brightness adjustment apparatus of the image reader according to the present invention.

1, a scanner controller 1 for generating a timing signal for performing a series of scanning operations and managing the operation of the overall system; A ROM 2 in which a program and reference data having a constant flow are stored so that the scanner controller 1 can control the scanner system in a predetermined order; A RAM (3) for storing temporary data generated while the scanner controller (1) controls the system; A lamp 4 for outputting three colors of R (red), G (green), and B (blue) to read the image information of the original with the amount of reflected light; A lamp driver 5 which receives a control signal from the scanner controller 1 at a suitable time to drive the lamp 4 and turns on and off the lamp 4; An optical module 6 for reflecting the three-colored light output from the lamp 4 to the original to perform color separation filtering to form an optical path to be incident on an image sensor corresponding to each color component; A step motor 7 which receives a drive signal from the scanner control unit 1 and moves the optical module 6 in the sub-scanning direction of the original according to a predetermined resolution; An image sensor 8 that photoelectrically converts color information of each of three primary colors B, G, and R into an electrical analog signal in proportion to the amount of light input through the optical module 6; A sensor driver 9 for supplying a clock signal to the image sensor 8 to receive a predetermined signal from the scanner controller 1 and to operate the image sensor 8, a red analog buffer 10a, and a green analog buffer 10b. A buffer unit 10 configured to include a blue analog buffer 10c to buffer an analog image signal acquired by the image sensor 8 to prevent distortion of the signal during signal processing; A multiplexer 11 for selectively outputting any one of analog image signals of each color component input from the buffer unit 10 according to a signal supplied from the scanner controller 1; An analog switch 12 for selecting an amplification degree suitable for an analog image signal of each color component output from the multiplexer 11; A signal amplifier 13 which amplifies the analog image signal having a low voltage output from the buffer unit 10 and amplifies it with an amplification selected by the analog switch 12 so as to be processed by a circuit at a later stage; A pre-processing unit 14 which receives the analog signal amplified by the amplifying unit 13, performs black and white correction processing, converts the analog amplified signal into digital image data, and outputs it; A memory buffer 15 for buffering the output of the preprocessor 14; And an interface unit 17 which transfers the image data stored in the memory buffer 15 to the computer 16 in accordance with a predetermined transfer standard.

On the other hand, FIG. 2 includes a timer 18 mounted in the scanner controller 1 shown in FIG. 1 to control the operation timing of the sensor driver 9; A detailed block diagram of the sensor driver 9 connected to the timer 18 and controlling the operation state of the image sensor 8 by the timing control signal output from the timer 18 is shown.

Herein, the detailed structure of the timer 18 includes: a latch unit 19 for latching the reference data detected from the ROM 2 for a predetermined time, a counter 20 for receiving and counting clock signals of a predetermined period; Compares the preset reference data output from the latch unit 19 and the counting value output from the counter 20, and outputs a trigger signal corresponding to one period input to the counter 20 when the reference data and the counting value are the same. Comparator 21 is included.

On the other hand, the sensor driver 9 includes a shift pulse generator 22 that generates a shift pulse signal at a constant interval (for example, 1 ms) by a trigger signal output from the comparator 21, such as a monostable multivibrator, and a shift pulse. And a drive clock generator 23 for generating drive clocks? 1,? 2, and RS of the image sensor 8 in accordance with the shift pulse signal output from the generator 22.

Referring to Figures 3 to 5 with respect to the operation of the present invention having such a configuration as follows.

The image sensor 8 transmits the signal charges accumulated and photoelectrically converted into a photo diode array to an analog shift register and sequentially reads them. Referring to the configuration of the image sensor 8 shown in FIG. 3, the image sensor 8 includes a photosensitive unit 24, a transmission unit 25, and an output unit 26. Here, the photosensitive portion 24 converts the light energy into an electrical signal, and temporarily accumulates the obtained signal charges. The transmitter 25 sequentially transmits the signal charges generated by the photosensitive unit 24 to the output unit 26. Clock pulses for transferring charge are typically used in two phases, which are easy to drive. The output unit 26 has a function of converting signal charges transmitted from the transmission unit 25 into voltage. When the signal charge from the transmission unit 25 is injected into the floating capacitor, the potential of the floating capacitor is changed, and the output capacitor is output to the source follower circuit of the MOS transistor.

Next, driving signals of the image sensor 8 shown in FIGS. 4A to 4E will be described.

4A shows a driving signal of the image sensor 8 as a shift pulse signal SH for moving charges accumulated in the photodiode array, which is the photosensitive unit 24, to the analog shift register, which is the transfer unit 25, and FIG. 4B and FIG. FIG. 4C shows clock signals φ1 and φ2 having opposite phases so that each pixel is sequentially output one pixel from a shift register. FIG. 4D shows each pixel in a floating capacitor in which signal charges output from an output terminal are converted into voltage. Is a reset signal (RS) that clears the following capacitor after the output is finally output from the floating capacitor to the source follower circuit. Here, the time T _INT from the falling edge SH to the next falling edge is the optical signal accumulation time, which is a reading time in the main scanning direction with respect to the original image. 4E shows a waveform of the output signal OS output according to the driving signal of the image sensor 8, and the output pixel has an effective pixel after the dummy pixel having a constant coefficient is output due to the structure of the image sensor. The output form is shown.

On the other hand, Figure 5 is a waveform diagram showing the photoelectric conversion characteristics of the sensor, showing that a constant output is obtained when the input light amount (illuminance × accumulation time) is constant, and when the straight portion is expressed by the equation shown in Equation 1 below .

y = ax ^r + b

Here, the slope a indicates the sensitivity (ratio of the output voltage amount to the input light amount), b is the output voltage (implicit output voltage) when the input light amount is 0 (implicit), and r is about 1. In addition, the input light amount at the refraction point of this characteristic curve is called a saturated exposure amount, which means that the output amount does not increase even if the light amount is increased any more. The saturation output amount at this time is called saturation output voltage (V _CE ).

In general, in the case of designing an optical system of an image reading apparatus that reads an image, in order to read an original image in a stable state, the final output of the image sensor 8 is 80 of the saturated output voltage V _CE of the image sensor 8. We design according to%. At this time, assuming that the illuminance of the lamp 4 serving as the light source is constant, the input light amount is defined as a function of the accumulation time, and an output voltage proportional to the optical signal accumulation time T _INT can be obtained. Therefore, in the present invention, by adjusting the optical signal accumulation time (T _INT ) by using the characteristics of the image sensor 8 as a variable to control the brightness of the step determined by the user.

In FIG. 5, it is assumed that the optical signal accumulation time T _{INT at} which the output voltage as the reference of the optical system design reaches 0.8 × V _CE is X1, and the optical signal accumulation time T _INT at the saturation voltage V _CE is X2. Assume that the optical accumulation time T _INT at which the output voltage reaches 0.6 x V _CE is X3, this time is the optical signal accumulation time representing the period of the shift pulse signal SH shown in Fig. 4A. Corresponds to (T _INT ).

At this time, assuming that the brightness of the output image is adjusted by setting 10 steps in the dark direction and 10 steps in the bright direction, the optical signal accumulation time (X) for each step may be defined by Equation 2 below.

However, as shown in Fig. 4E, X3 should be configured to have a time longer than the time for outputting the number of pixels plus the dummy pixel and the effective dummy pixel.

Next, a process of generating a shift pulse signal SH corresponding to the optical signal accumulation time T _INT determined by Equation 2 as described above will be described. The optical signal accumulation time T _INT determined by Equation 2 above is programmed and stored in the ROM 2 shown in FIG. The driving signal of the image sensor 8 is generated by the sensor driver 9 and is controlled by a clock signal and a trigger signal of a constant period provided by the timer 18 shown in FIG.

That is, as shown in FIG. 2, a clock signal of a predetermined period is input to the counter 20, and the output of the counter 20 is input to the comparator 21. The reference data output from the scanner controller 1 is latched through the latch unit 19 and then input to the comparator 21. When the output value of the counter 20 constantly increases and coincides with the value of the preset reference data, the comparator 21 outputs a logic 'low' signal corresponding to one cycle of the clock input to the counter 20. The signal output from the comparator 21 is set as the reference signal for setting the counter 20 to 0 and at the same time as the trigger signal of the shift pulse generator 22. The shift pulse generator 22 generates a pulse signal of a predetermined period which is triggered by the output signal of the comparator 21 and maintains a logic 'high' state at regular intervals. In synchronization with this signal, the sensor driver 9 generates respective drive signals as shown in Figs. 4A to 4D.

The optical signal accumulation time T _INT determined by Equation 2 above is converted into reference data provided by the scanner controller 1 as an input of the comparator 21, and appropriate reference data values according to the brightness level determined by the user. It is set to and input to the comparator 21.

Therefore, by changing the optical signal accumulation time TINT of the image sensor 8, the brightness of the image can be adjusted.

Meanwhile, in the present invention, the light direction and the dark direction have been set in 10 steps, respectively. However, according to the capability (precision) of the timer 18 included in the scanner control unit 1, it can be divided into more steps.

As a result, according to the brightness adjusting method and apparatus of the image reader according to the present invention, there are advantages as follows.

(1) By setting a simple circuit configuration to enable various levels of brightness adjustment, an output image reflecting the brightness adjustment can be obtained in synchronization with the read operation of the image. Thus, processing time for executing a separate image editing program is required. Real time processing is possible.

(2) Brightness is adjusted by changing the light signal accumulation time of the light source which is proportional to the output voltage of the image sensor, so it is possible to precisely adjust the brightness reflecting the characteristics of the light source, and no additional correction is required according to the change of light source over time. .

(3) Since brightness is adjusted in analog area, not digital area, accurate brightness can be adjusted without adding additional circuit means or reference data.

(4) It is possible to obtain a contrast effect of contrast due to brightness adjustment without dropping the gradation due to digital processing and to obtain a clearer image.

(5) Brightness adjustment is performed by changing the light accumulation time, so that when the image output in the dark direction is obtained, the read operation is possible faster than in the standard state, so that the result of the brightness adjustment can be confirmed quickly.

Claims (13)

In the brightness adjustment method of the image reader which converts the optical density of the original input to the image sensor into an analog image signal through a photoelectric conversion method, and after performing a pre-processing, and converts into digitized image data: An input step of receiving reference data set by a user; A comparison step of comparing the counting value counted at an arbitrary period with the reference data input in the input step; A conversion step of converting the counting value to a time value if the result compared in the comparing step is the same; And And adjusting the brightness of an image by adjusting an accumulation time of an optical signal input to the image sensor in response to the converted time value. The method of claim 1, wherein the comparing step, And generating a clock signal having a predetermined frequency, counting the clock signal to detect a counting value, and comparing the detected counting value with the reference data. The method of claim 2, wherein the frequency of the clock signal, And a brightness coefficient of the image reader corresponding to the division coefficient of the brightness adjustment step divided into a plurality of parts to adjust the brightness of the image. The method of claim 1, wherein the adjusting step, After counting the clock signal, the optical signal accumulating operation is continued until the reference data and the counting value are the same. If the reference data and the counting value are the same, the counting value is initialized. And a brightness adjusting method of the image reader which resumes the optical signal storing operation. The method of claim 1, wherein after performing the adjusting step, And a setting step of setting and storing the reference data, and adjusting the brightness of the image in response to the set and stored reference data unless a user inputs the reference data. In the brightness control device of the image reader for converting the optical density of the original input to the image sensor into an analog image signal through a photoelectric conversion method, and after performing a pre-processing, to convert to the digitized image data: A scanner controller for detecting a time value corresponding to the reference data input by the user and outputting a predetermined control signal for controlling the accumulation time of the optical signal input to the image sensor according to the detected time value; And And a sensor driver for controlling a driving state of the image sensor according to a predetermined control signal from the scanner controller. The method of claim 6, wherein the scanner control unit, And a timer for controlling the start and end point of accumulation of the optical signal in response to the reference data. The method of claim 7, wherein the timer, A latch unit for latching the reference data for a predetermined time; A counter for receiving and counting a clock signal having a predetermined frequency; And Comparing whether the reference data latched by the latch unit and the counting value counted by the counter are equal to each other. If the reference data and the counting value are the same, a trigger signal having a predetermined period indicating the start and end point of accumulating the optical signal is generated. And a comparator for generating and outputting the comparator to the sensor driver. The method of claim 8, wherein the predetermined frequency of the clock signal, And a brightness adjustment device of the image reader corresponding to the division coefficients of the brightness adjustment step divided into a plurality so as to adjust the brightness of the image. The method of claim 8, wherein the trigger signal, And a pulse signal of a period corresponding to one period of the pulse signal input to the counter. The method of claim 6 or 8, wherein the sensor driver, A shift pulse generator for generating a shift pulse signal of a predetermined period by the trigger signal output from the comparator; And And a drive clock generator for generating a drive clock of the image sensor in response to the shift pulse signal output from the shift pulse generator. The method of claim 11, wherein the drive clock, And a first driving clock and a second driving clock, wherein the first driving clock and the second driving clock have a phase difference of 180 ° with each other so as to alternately read the pixels of the image. The method of claim 11, wherein the drive clock, And a reset signal, wherein the image sensor initializes the accumulation state of the optical signal by the reset signal.